2009 Annual Report
1a.Objectives (from AD-416)
Research proposed in this project includes both basic and applied research evaluating the impact of agricultural practices (tillage, residue management, soil fertility, and crop rotation) on soil productivity and crop yield and quality. Specific objectives include:.
1)Measure the effects of tillage, residue management, fertility, and crop rotation on physical, chemical, and biological properties of soils in agricultural crop production systems..
2)Develop crop rotation, nutrient, soil, residue, and pest management practices that improve farming efficiency (increase unit output/unit input), maintain or increase soil productivity, and improve crop yield and quality..
3)Measure the effects of corn stover/residue removed for biofuel feedstock on: (1) short-term balances of soil C and N; (2) crop yield and quality; and (3) soil resource condition.
1b.Approach (from AD-416)
Established long-term field experiments evaluating the effect of crop rotation, residue management, fertility and tillage will be utilized to evaluate the research hypothesis that crop rotations, crop diversity, and crop sequence improves soil quality and productivity and that increased crop diversity, attained through the introduction of alternative crops and improved crop sequences into the traditional corn/soybean rotation, will improve crop yield and quality while maintaining or improving soil quality. To address the hypothesis that no significant effect of genetic modification of corn genotype on soil microbes (DNA compositional measures) and their processes (e.g., C&N transformations) will be detectable, a field experiment will be established evaluating several different corn isolines with and with out genetically modified organisms. To evaluate the hypothesis that cover crops and integrated weed management strategies will increase biodiversity and enhance sustainable crop production, research will be conducted in two phases. Phase 1 will consist of a small-plot field experiment in which different species of grasses and legumes will be evaluated as cover crops in a corn/soybean/spring wheat rotation. The viability of cover crops as a management tool for weeds and insects relative to chemically-driven pest management will be investigated in Phase 2 of the research. Field and greenhouse experiments will be established evaluating a number of different soybean genotypes to test the hypothesis that soybean genotypes with significantly more root length and mass in the top 10 cm of soil (extensive fibrous root system) will have a more positive impact on soil organic matter, aggregate stability, and soil strength than other soybean genotypes.
Studies of the decomposition of Bt corn residue relative to non-Bt corn residue by using corn residues collected from plots experiencing insect pressure have been extended. During this past year, two multi-year studies were completed that showed no differences in the decomposition of Bt and non-Bt corn residues, even when differential insect damage to the corn plants was evident.
Three years of data have been obtained and are being analyzed and evaluated to determine the impact of incorporating cover crops into a corn/soybean wheat rotation on improving crop yield, quality, trafficability and nitrogen mineralization dynamics.
Evaluation of the environmental sustainability of alternative production practices continues via measuring greenhouse gases (CO2, CH4, N2O) fluxes, soil carbon dynamics and soil quality indicators. This research is part of a nationwide ARS network: GRACEnet and REAP cross locations research projects.
Soybean has less root length and mass in the top 10 cm of soil than other crops such as corn. This causes soybean fields to be more prone to have soil erosion and reduced soil productivity. A few soybean genotypes have been identified that have had more root length and mass in the top 10 cm of soil. If these genotypes have consistently more root mass and length in more environments they can be used by soybean breeders that want to develop varieties that can contribute to improving soil productivity.
Optimization and Validation of Advanced Method for Measuring Soil Microbial Activities. Soil microorganisms are essential to the functioning of agricultural soils, yet current methods to measure their activities have severe limitations. The lack of an inexpensive, easy to use measurement approach for soil microbial activities hampers attempts to understand the complex linkages among compartments (e.g., soils, plants, and soil microbes) in agricultural systems. In 2008, we completed and published (ARIS # 226397) a series of experiments that optimize a novel assay of microbial activities and validates the use of this assay with agricultural soils. Our results document the utility and the advantages of this respiration-based assay of soil microbial activities and promote its use by other researchers. By providing an effective means of measuring soil microbial activities, there is opportunity for advancing understanding of the ecological relationships in agricultural systems. With adequate knowledge, agricultural management practices can be adjusted to achieve maximum economy and environmental sustainability.
Crop Rotation as a Substitute for Fertilizer Nitrogen in Corn Production. Complex crop rotations, once extensively used by farmers, have been supplanted by intensive monoculture or short rotation cropping in many areas of the US. ARS scientists in Brookings, South Dakota and Morris, Minnesota, in collaboration with South Dakota State University, conducted long-term experiments to investigate the effects of complex crop rotation containing forage legumes on soil fertility, corn yield and nutrition. Corn grain yield was stable across all N input levels studied in rotations where corn followed a forage legume. Conversely, corn yield decreased as N input level was reduced under the continuous corn and corn-soybean rotation treatments. Our data suggest that substitution of complex crop rotation for fertilizer nitrogen in corn production may be an environmentally and economically sustainable practice. This information was transferred to corn producers, extension agents, and other scientists through professional journal articles and presentations to user groups.
Improving Soil Quality and Crop Yield utilizing Cover Crops. The benefits of cover crop have been known for decades, but they have been underutilized in part due to the low cost of agricultural inputs. As input costs continue to rise producers are reexamining the use of cover crops within their production system as a source of weed, insect and disease suppression and as a green manure. Research has been conducted to evaluate the impact of utilizing cover crops within complex no-till crop rotation systems. Results show that incorporation of cover crops improves trafficability, increases in-season nitrogen availability, and decreases pressures from crop pests. These results have been transferred to South Dakota NRCS to provide information for the development of the Cover Crop Tech Note #16, and help determine eligible producers for EQIP funds for cover crops.
Improving Soil Quality Indicators Under No-Tillage. Ten years of no-tillage increased soil organic carbon in the top 50 mm by 9% compared to conventional tillage and the increase in soil organic carbon corresponded to marked improvement in soil properties and quality (fine particulate organic matter, water stable aggregates, increase in basidiomycete fungi (decomposers of cellulose and lignin in nonliving organic matter). We conclude that the soil environment under no-tillage is highly conducive to particulate organic matter accumulation (through plant root systems that remain undisturbed by tillage) and thus the greater population of fungi under no-tillage compared with conventional tillage. Differences in decomposition of organic material under these two tillage systems resulted in unique chemical constituents of soil organic matter. In northern sub-humid regions of the Great Plains, wind and water erosion are persistent problems. Tillage practices such as no-till that improve soil aggregate stability will help retard soil loss by maintaining surface conditions resistant to erosive forces.
Native Grass Management Methods for Increased Soil Carbon Accumulation. Increasing soil carbon concentration improves soil water infiltration, reduces soil erosion, and stabilizes crop yield. ARS scientists at Brookings, South Dakota, in collaboration with South Dakota State University, are conducting long-term field studies to evaluate grass canopy management methods and grass species mixture effects on soil carbon accumulation in soils previously farmed under row crops. Annual spring burning as a grassland management treatment was detrimental to the accumulation of soil C as well as to the growth of cool season grasses when compared with no canopy management. Mow and remove management (which would be compatible with cellulosic biomass production) showed values of soil C accumulation intermediate between those seen under the spring burn and no management treatments. This advancement of knowledge of grass management options was transferred to farmers at annual field days and to other scientists at an international meeting on soil organic matter.
Impact of Crop Rotation on Soil Carbon and Soil Quality. Corn captures significant amounts of carbon; however, only a small fraction of plant carbon may be retained in the soil. Research was conducted to evaluate the effect of crop rotation and nitrogen fertilization under conventional tillage on soil carbon sequestration. Continuous corn returned about 34% more plant carbon to the soil compared with the four-year rotation of corn-soybean-wheat-alfalfa. Yet, soil organic carbon loss under continuous corn was nearly tenfold greater than the four–year rotation. Soil productivity is related to both quantity of soil organic carbon and quality of soil organic matter as well as other factors. The plant integrates across many biological, chemical, and physical soil properties and the historic good yield of corn on the four-year rotation may reflect soil-improvement from this rotation. Our findings on carbon storage are relevant to the northern Corn Belt as an estimate to reasonable rates of soil organic carbon accumulation or loss.
Pikul, Jr., J.L., Chilom, G., Rice, J., Eynard, A., Schumacher, T.E., Nichols, K., Johnson, J.M.F., Wright, S., Caesar, T., Ellsbury, M. 2009. Organic Matter and Water Stability of Field Aggregates Affected by Tillage in South Dakota. Soil Science Society of America Journal. 73:197-206.
Pikul Jr, J.L., Johnson, J.M., Schumacher, T., Vigil, M.F., Riedell, W.E. 2008. Change in Surface Soil Carbon Under Rotated Corn in Eastern South Dakota. Soil Science Society of America Journal. 72:1738-1744.
Lehman, R.M., Osborne, S.L., Rosentrater, K.A. 2008. No Evidence that Bt Genes and their Products Influence the Susceptibility of Corn Residue to Decomposition. Agronomy Journal. 100:1687-1693.
Zabaloy, M.C., Lehman, R.M., Frey, S.D., Garland, J.L. 2008. Optimization of an oxygen-based approach for community-level physiological profiling of soils. Soil Biology and Biochemistry. 40(12):2960-2969.
Lehman, R.M., Lundgren, J.G., Petzke, L.M. 2009. Bacterial Communities Associated with the Digestive Tract of the Predatory Ground Beetle, Poecilus chalcites, and Their Response to Laboratory Rearing and Antibiotic Treatment. Microbial Ecology. 57:349-358. Available online.
Riedell, W.E., Pikul Jr, J.L., Jaradat, A.A., Schumacher, T.E. 2009. Crop Rotation and Nitrogen Input Effects on Soil Fertility, Maize Mineral Nutrition, and Seed Composition. Agronomy Journal. 101:870-879.